A method is presented for the preparation of a sensitive and diagnostic stained antigen for the detection of fowls suspected of infection by the organisms found in epidemic bacillary white diarrhoea (pullorum disease).

Evidence is presented that an antigen prepared from organisms grown in a medium which provides for the peculiar growth requirements of the anaerobic organism associated with anaerogenic pullorum, is more sensitive than antigens prepared from organisms grown on media which lack these peculiar growth factors.

A stained antigen has been prepared which is agglutinated by pullorum antisera in 15 sec. at 4°C. and in 6 sec. a t 15°C. and which is not agglutinated by normal sera in 5 min.

The author wishes to thank the Directors of Messrs J. Bibby and Sons, Ltd., for permission to publish these papers.

In particular he would thank Mr J. Pye Bibby for his keen interest in the investigations and for his loyal support throughout.

In addition he wishes to thank Miss Margaret Davies for her assistance in the bacteriological investigations, and Miss Margaret Shafto for laboratory work and the compilation of relevant data.